(1) Field of the Invention
This invention relates to a growth promoter for Bifidobacterium species. More particularly, it relates to a growth promoter for Bifidobacterium species comprising gourd food of yugao gourd as the active ingredient, and a method of using such a growth promoter.
(2) Description of the Prior Art
Bacteria of the genus Bifidobacterium have no pathogenicity and occur principally in the intestine of man. It has been established that they have a physiological significance in the suppression of formation of intestinal putrefaction products and the improvement of diarrhea or constipation. Moreover, it has recently been reported that they enhance immunity, prevent the replacement of bacteria as encountered during continuous administration of antibiotics, and suppress the activity of carcinogens, and this has led to their wide applications in clinical fields ("Microorganisms", Vol. 1, No. 4, Igaku Shuppan Center). Thus, Bifidobacterium species are very important from the viewpoint of health and therapeutics.
There are two methods for growing Bifidobacterium species in the intestine. One of them is the direct method in which cells of Bifidobacterium species are administered orally, and the other is the indirect method in which a substance utilizable by Bifidobacterium species (hereinafter referred to as "bifidus factor") is administered to promote the growth of Bifidobacterium species. The direct method is disadvantageous in that the stability of Bifidobacterium preparations is poor and the degree of colonization of administered Bifidobacterium species is low. Accordingly, instead of the direct method, more importance has recently been attached to the indirect method in which a bifidus factor is orally administered to promote the growth of Bifidobacterium species in the intestine.
Conventionally, a variety of substances are known to act as bifidus factors. Specific examples thereof include N-acetylglucosamine and its derivatives, carrot extract (principally containing pantetheine), lactulose, raffinose, stachyose, maltotriose ("Bifidus Bacteria", Yakult Co., Ltd., 1979), fructooligosaccharide ("Kagaku-to-Seibutsu", Vol. 21, p. 291, 1983), galacto-oligosaccharide [U.S. Pat. No. 4,435,389 (U.K. Pat. 2,080,330; Japanese Patent Publication No. 20266/'83); Japanese Patent Publication No. 46479/'86; Japanese Patent Laid-Open No. 41449/'85], isomalto-oligosaccharide (a report presented at a meeting of the Japanese Society of Dietetics and Food Science, 1986), cyclodextrin [U.S. Pat. No. 4,451,457 (U.K. Pat. 2,092,890; Japanese Patent Laid-Open No. 138385/'82)], mannan from devil's tongue ("Riken Intestinal Flora Symposium III, Intestinal Flora and Nutrition", Gakkai Shuppan Center, p. 89, 1983), soybean milk (Japanese Patent Publication No. 9822/'70; Japanese Patent Laid-Open Nos. 142566/'76 and 85390/'80), soybean milk extract (Japanese Patent Laid-Open No. 179064/'84), an extract from a culture of non-pathogenic Escherichia species (Japanese Patent Publication No. 13359/'75), and the like.
The term "gourd" is a generic name for plants belonging to the family Cucurbitaceae, which family includes the genus Lagenaria and the genus Cucurbita.
The term "yugao" refers to bottle gourd or white flower gourd, an annual crawling plant of the family Cucurbitaceae whose botanical name is Lagenaria siceraria Standl. var. hispida Hara or Lagenaria leucantha Rusby var. clavata Makino (Illustrated Horticultural Flora In Colour, 1984, p. 440-445, Hokuryukan Co., Ltd., Tokyo, Japan; and Makino's Picture Book of Japanese Plants, Hokuryu-Kan, 1967 and 1969, p. 38-41).
The term "togan" or "kamouri" (both of which are synonymous) refers to wax gourd, an annual crawling plant of the family Cucurbitaceae whose botanical name is Benincasa hispida Cogn. or Benincasa Certifera Savi, and whose fruit, skin and seeds have long been used for their anti-inflammatory and diuretic activity.
For instance, the fruit of wax gourd may be dried and crushed, and then combined as is, or as its ethanol or water extract, with the spray dried steam extract of the soluble components of the leaf, stalk and other above ground parts to form a health tea (Japanese Patent Laid-Open No. 239875/'87). Also, the fruit of wax gourd may be sterilized, and after removing the seeds, extracted with aqueous solvent and the extract spray dried to form a powder combined with fermented tea leaves, i.e. Thea Shinsesis, and other ingredients to form an eye health tea for fatigued eyes caused by poor blood circulation or by hypoglycemia (Japanese Patent Laid-Open No. 56436/'87).
Yugao gourd (plant of the genus Lagenaria) is distinct from other gourds of the family Cucurbitaceae, such as togan (wax gourd), directly edible plants (U.S. Pat. No. 3,219,542 to Lammers) as exemplified by pumpkin, squash, cucumber and watermelon (Encyclopedia Americana, Intl. Ed. 1987, vol. 13, p. 125), and Buffalo gourd, a perennial plant of the genus Cucurbita whose botanical name is Cucurbita foetidissimo HBK (Chemical Abstracts, 84:149505k, 1986; and 93:235075n, 1980).
In Japan, yugao gourds have been eaten as food from olden times. Dried gourd shavings of yugao gourd are called "kanpyo" or "kampyo" (both of which are synonymous) and have long been used popularly as ingredients of sushi, plain dishes and the like. Yugao gourds are a highly nutritious food containing a well-balanced combination of sugars, fibers, protein, vitamins, calcium, pectin and the like. Moreover, it has recently been reported that gourd food lessens the influence of the human body of Amaranth (Red No. 2) used as a food dye, and has the effect of preventing the blood cholesterol level from rising (Annual Report on the Opening-up of New Markets and the Realization of Vision for the Year 1985, Tochigi Prefecture Gourd Trade Association).
Thus, there is an increasing demand for gourds as a healthful food ("My Health", Shufu-no-Tomo Co., May issue, 1986). Furthermore, yugao gourds are an important agricultural product in the whole area of Tochigi Prefecture, Japan, and it is eagerly desired to utilize them to the fullest extent.
However, it has not been known that gourd food made from yugao gourd promotes the growth of Bifidobacterium species.
Since dried gourd shavings of yugao gourd (kanpyo) have a water content of as high as 15 to 40% in themselves and, moreover, are a highly nutritious food, in time they tend to grow bacteria, mold and the like, and to turn brown in color. Thus, 3 or 4 months after preparation, they suffer an adverse change in properties (such as color, odor, taste, etc.) and quality. For this reason, much care has been required for storage thereof.
In order to keep the quality of dried gourd shavings, there has been proposed a method in which the flesh of a gourd is sliced into ribbons, dried and then fumigated with sulfur, e.g. as sulfurous acid or sulfur dioxide, for bleaching and sterilizing purposes [Japanese Patent Publication No. 21292/'82; "Food Industry", Vol. 3, Book II, p. 52 (1982)]. However, this method unavoidably causes the occurrence of residual sulfur. As sulfur is very harmful to human beings and the presence of any residual sulfur is undesirable, its presence in food is regulated (cf. the Food Sanitation Act of Japan). Thus, the sulfur fumigated and bleached dried gourd shavings must be washed in water prior to eating, which causes most of the water soluble nutrients (such as sugars, pectin, vitamins, etc.) therein to be washed away. Similarly, a gourd food made by reducing such dried shavings to powder is also deprived of most water soluble nutrients.
The sulfur fumigated and bleached kanpyo has to be well steeped in water, then boiled and thereafter washed extensively to remove residual sulfites. The gourd shavings turn brown upon being boiled, and up to about 60% of the nutrients, comprising almost 100% of the water soluble nutrients, are undesirably lost consequent the required sulfur constituent removal washing.
In one teaching, the fruit of yugao gourd that has been dehydrated, dried and pulverized to form a powdery product, is said to have the unique taste and flavor of gourd and high nutritive value for use with wheat flour or other raw material in making noodles, tofu (soybean curd), confectionary (cake), etc. (Japanese Patent Laid-Open No. 132868/'84). The dehydrating method is not indicated, but yugao gourd fruit (about 95% water content) is normally only dehydrated by press-squeezing the dried shavings (kanpyo) to express therefrom the 15 to 40% remaining moisture content, thus washing away the major nutrient content.
In a further teaching, the outer skin, including the attached pulp and core containing the seeds, is removed from initial or middle stage growth harvested yugao gourd, the obtained pulp is cut into small pieces and blanched by boiling for 10 minutes under undisclosed boiling conditions, the boiled pieces then frozen to induce partial disruption of the cell membranes and denature the tissue, followed by thawing at room temperature, dehydrating, drying and pulverizing of the pieces, for use as raw material for confectionary (cake) or as dietary fiber (Japanese Patent Laid-Open No. 96966/'86). Subjecting yugao gourd fruit flesh to this type of degrading treatment fosters formation of a three dimensional network structure that retains a large quantity of water and assumes a semi-gel form. This enables the degraded gourd pulverized product to increase the formability of confectionary or other food when included with the other ingredients in preparing the food.
However, blanching or boiling of yugao gourd fruit causes major loss of its water soluble nutrients and edible fibers, and further loss thereof occurs upon dehydrating yugao gourd fruit, which is normally only effected by press-squeezing the dried shavings to express the retained moisture content therefrom.
In a still further teaching, commercial dried gourd shavings (kanpyo) are boiled in water or steeped and then steamed, to form an instant food for use in cooking upon regeneration with hot water (Japanese Patent Laid-Open No. 219349/'87). The boiling or steeping and steaming, serves to remove sulfur residue consequent earlier sulfur fumigating and bleaching of yugao gourd dried shavings (kanpyo) in preparing the commercial gourd shavings. Hence, the water soluble components in the dried gourd shavings, i.e. the nutrient components, including sugars, vitamins, amino acids and minerals, and edible fibers, are washed away.
In order to overcome the above described disadvantages, there has been proposed a gourd food of yugao gourd (unbleached dried gourd) made without bleaching by fumigation with sulfur. This gourd food is quite safe from the viewpoint of food sanitation, is highly nutritious, and has good keeping quality, so that it can be eaten for nourishing purposes, i.e. as a food itself, as is, in normal nourishing or hunger satisfying quantities or bulk amounts (Japanese Patent Laid-Open No. 32458/'88). The underlying objective of this teaching is to combine the unbleached dried gourd, as is, with another food to impart the taste and modifying characteristics of the other food thereto in view of the peculiar grassy smell, characteristic bitter strong taste, stickiness property, etc. of the yugao gourd from which it is made, thereby making the gourd itself easier to eat. The optimal amounts used are selected to provide the unbleached dried gourd in a nourishing amount with the other food.
It is also known that unbleached dried gourd (yugao) has a neutral detergent fiber (NDF) content of about 30% (Japanese Patent Laid-Open No. 32458/'88). NDF is a typical food fiber, and it is well known that people taking plenty of food fibers have a low incidence of rectal cancer.
The above-described conventional bifidus factors have the disadvantage that, in the living body, they are also utilized by other intestinal bacteria such as lactic acid bacteria and are not sufficiently effective in promoting the growth of Bifidobacterium species. Moreover, the processes for preparing these bifidus factors are tedious and/or they are expensive. Accordingly, it is desired to develop a bifidus factor which is selectively utilized by Bifidobacterium species in the living body and can effectively promote the growth thereof. Moreover, if such a bifidus factor is cheap and easy to obtain or prepare, its utility will become still greater.